This study will evaluate the hypocholesterolemic effects and influence on cholesterol biosynthesis of simvastatin and fluvastatin in 25-30 patients with moderate primary hypercholesterolemia. After a five week dietary baseline, patients will receive active drug therapy with three potential doses of simvastatin (5, 10, or 20 mg/day) or fluvastatin (20 or 40 mg/day). Patients will receive three of these five treatment options each for a period of five weeks.